Tourmaline: Maine's State Mineral

Tourmaline: Maine's State Mineral

Tourmaline is one of the most attractive minerals occurring in Maine. It ranges in color from black or white to vibrant shades of red, green, and blue. The color of the best Maine specimens rivals that of tourmaline from world-famous localities in California, Brazil, and the Himalayas. Individual crystals range from opaque to transparent and may be single or multi-colored. There is even a "watermelon" variety with a green outer layer surrounding a pink core. Transparent crystals that are clear enough to yield faceted gemstones are highly prized, while lesser grades of this durable mineral are tumble-polished for use in various kinds of jewelry. Well-formed tourmaline crystals in their natural state are also sought by mineral collectors.

Tourmaline is actually a group of several different minerals which have similar crystal structures, but complex and variable chemical formulas. The exact species of tourmaline is determined by which of a number of possible elements are present. The most common species in Maine is schorl, a black, iron-bearing tourmaline. The colorful, but less common, species found in Maine is elbaite, named after the island of Elba, Italy. Tourmaline occurs as lustrous, elongate crystals which commonly have a rounded triangular cross section and narrow grooves running parallel to their long direction. The crystals range in size from microscopic to over a foot long. The best examples in Maine are found in a very coarse-grained type of granite called "pegmatite." The slow cooling and solidification of the pegmatite veins allowed the mineral grains to grow to much larger sizes than in ordinary granite. The black tourmaline crystals and many of the brightly colored ones are usually encased in the surrounding rock. However, conditions in some places favored the development of open cavities in which elbaite crystals grew with greater perfection and clarity. These pegmatite "pockets" are the source of Maine's finest gem tourmalines.

Tourmaline Discoveries in Maine

The first major tourmaline discovery in Maine occurred in 1820 at Mount Mica in Paris. The famous story of the discovery by two boys exploring the local countryside was related by Augustus Hamlin in his 1895 book entitled "The History of Mount Mica." A quarry that was opened at the site has intermittently produced gem tourmaline and other interesting minerals up to the present day. The Hamlin Necklace, containing fine tourmalines of various colors from this quarry, can be seen in the Harvard University Mineralogical Museum.

Many other tourmaline deposits have been found in Maine over the years. Sharp crystals of black tourmaline are widespread in pegmatites of Oxford, Androscoggin, Sagadahoc, and Cumberland Counties. The colored crystals occur mainly in Oxford County and the Auburn-Poland area. It is curious that the best gem-producing localities lie on a straight line extending southeastward through this part of the state. In 1972 a spectacular series of large tourmaline pockets was opened at the Dunton Mine in Newry. Hundreds of pounds of red and green crystals were found, including the "Jolly Green Giant," a 10-inch crystal now in the collection of the National Museum of Natural History in Washington, D.C. The State of Maine tourmaline necklace was designed using Newry gems and presented to the State in 1975 by the Maine Retail Jewelers Association. (The chain of this necklace was made from gold nuggets panned from the Swift River in Byron.)